Phase-shift mask and method of forming the same

ABSTRACT

In an attenuated phase-shift mask (PSM) and a method of forming the same, a phase-shift layer and a light-shielding layer are sequentially stacked on a transparent substrate. The phase-shift layer and the light-shielding layer are sequentially removed from the substrate, to form a light-shielding pattern including a first opening and a phase-shift pattern including a second opening that is connected to the first opening and partially exposes the transparent substrate. Then, a transmitting portion is formed through the light-shielding pattern by partially removing the light-shielding pattern. The transmitting portion includes at least one portion of the phase-shift pattern on which a transmittance controller is formed. In one embodiment, the transmittance controller comprises a metal having a high absorption coefficient, and is formed through sputtering and diffusion processes. Accordingly, the intensity deviation between 0 th  and 1 st  order beams may be decreased, to thereby improve the processing margin of the exposure process.

RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 12/002,275, filed on Dec. 13, 2007, which claims priority toKorean patent application number 10-2006-0127625, filed on Dec. 14, 2006in the Korean Intellectual Property Office, the contents of whichapplications are incorporated herein in their entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Example embodiments of the present invention relate to a phase-shiftmask (PSM) and a method of forming the same. More particularly, exampleembodiments of the present invention relate to an attenuated PSM forminimizing an intensity difference between a 0^(th) order beam and a1^(st) order beam, and a method of forming the same.

2. Description of the Related Art

As semiconductor devices continue to become more highly integrated,design rules for the devices are becoming gradually reduced. so that thecritical dimensions (CDs) of the semiconductor devices are currentlybecoming scaled down to about 0.07 μm, or less. The above reduction ofthe design rules and the CDs necessarily causes the various patterns forthe semiconductor devices to have high resolution.

Various resolution enhancement technologies (RETs) have been applied toprocesses for manufacturing semiconductor devices so as to formhigh-resolution patterns. For example, methods have been suggested forincreasing the numerical aperture (NA) of a lens so as to irradiateillumination light onto a minute area of an object in an exposuresystem, and improving the illumination light to have a short wavelengththrough a dipole or a cross-pole illumination process. Particularly, akrypton fluoride (KrF) excimer laser having a wavelength of about 248nm, an argon fluoride (ArF) excimer laser having a wavelength of about193 nm and a fluorine (F2) excimer laser having a wavelength of about157 nm are widely used as the illumination light of the exposure systemin accordance with the technical trend of high-integration degrees ofsemiconductor devices. Accordingly, the resolution of a pattern may besufficiently increased by using short-wavelength light as theillumination light. However, the short wavelength light also causesdeterioration of depth of focus (DOF) in an exposure process. For thatreason, the RETs commonly adopt a phase-shift mask (PSM) so as to avoiddeterioration of the DOF. An initial PSM includes various steppedportions that are formed or arranged in a transparent substrate, andthus the phase of the light penetrating through the PSM is shifted bythe stepped portions. However, more recent PSMs have been configured toinclude an additional layer that is formed on a transparent substrate,and thus the phase of the illumination light is shifted by theadditional layer. Particularly, an attenuated PSM has been widely usedfor forming a large-aspect-ratio pattern such as a contact hole, or anisolation pattern.

The attenuated PSM may shift the phase of the illumination light andcontrol the transmittance of the illumination light using a single layeror a double layer in such a manner that the intensity of a 0^(th) orderbeam becomes similar to that of a 1^(st) order beam of the illuminationlight. As a result, the attenuated PSM allows an object to undergo auniform exposure in an exposure system. A 2^(nd) order or higher beam ofthe illumination light may hardly be irradiated onto the same positionas the 0^(th) order beam due to the recent reduction in pattern sizes.For that reason, the light intensity of an illumination site on theobject is generally estimated based on the 0^(th) and 1^(st) order beamsof the illumination light. That is, when an intensity difference(hereinafter referred to as intensity deviation) between the 0^(th) andthe 1^(st) order beams is within an allowable range, the 0^(th) and the1^(st) order beams irradiated onto an exposure site of the object may besubstantially treated as a single beam having a uniform intensity, andthus a circuit pattern on a mask may be accurately transcribed onto theobject.

However, the recent reduction of CDs and pattern sizes of semiconductordevices may also cause a decrease of the transmission area of theattenuated PSM, to thereby increase the intensity deviation between the0^(th) and the 1^(st) order beams. As a result, the solubility of afirst portion of the exposure site onto which the 0^(th) order beam isirradiated can be different from that of a second portion of theexposure site onto which the 1^(st) order beam is irradiated, and thusthere is a problem in that the circuit pattern on the mask may not beaccurately transcribed onto the object.

FIG. 1 is a graph showing intensities of the 0^(th) and the 1^(st) orderbeams diffracted by a conventional attenuated PSM. In FIG. 1, thevertical axis represents beam intensity, and the horizontal axisrepresents a pattern size.

Referring to FIG. 1, as the pattern size becomes smaller, the intensitydeviation between the 0^(th) and the 1^(st) order beams becomes greater.Particularly, as the pattern size decreases, the intensity of the 0^(th)order beam is decreased and the intensity of the 1^(st) order beam isnot substantially changed. As a result, as the pattern size decreases,the intensity deviation is increased. Particularly, the intensitydeviation when the pattern size is about 40 nm is about two times theintensity deviation when the pattern size is about 100 nm.

In an effort to decrease the intensity deviation between the 0^(th) andthe 1^(st) order beams, there has been suggested that a phase-edge PSM(PEPSM), which compensates for a phase shift at an edge of alight-shielding pattern, or a chromeless mask (CLM), be used in place ofthe attenuated PSM. However, there is a problem in that use of the abovePEPSM or CLM requires an additional process, which can decrease processefficiency in a manufacturing process of a semiconductor device.

SUMMARY OF THE INVENTION

Accordingly, embodiments of the present invention provide a phase-shiftmask (PSM) for decreasing an intensity deviation between the 0^(th) andthe 1^(st) order beams at an exposure site of an object. An improvedattenuated PSM is provided, in which the intensity deviation issufficiently decreased at the exposure site of the object, despite sizereduction in a light-shielding pattern.

Embodiments of the present invention also provide a method ofmanufacturing the above PSM.

According to an aspect of the present invention, there is provided a PSMincluding a transmittance controller. The PSM includes a transparentsubstrate through which light passes, a light-shielding pattern that ispositioned on the transparent substrate and may prevent the light frombeing incident onto the transparent substrate, a phase-shift patternthat is positioned on the transparent substrate exposed through thetransmitting portion and a transmittance controller that is positionedat an upper portion of the phase-shift pattern in the transmittingportion. The light-shielding pattern defines a transmitting portionthrough which the transparent substrate is partially exposed and thelight is incident onto the transparent substrate, and the phase-shiftpattern shifts the phase of the light that passes through thetransmitting portion. The transmittance controller controls thetransmittance of the light with respect to the phase-shift pattern inthe transmitting portion.

In some example embodiments, the transmitting portion has a shapecorresponding to a circuit pattern that is to be transcribed onto asemiconductor substrate for manufacturing a semiconductor device, andthe phase-shift pattern comprises molybdenum (Mo) and thelight-shielding pattern comprises chromium (Cr). The transmittancecontroller can include a material selected from the group consisting ofchromium (Cr), molybdenum (Mo) and tungsten (W), and controls thetransmittance of the light passing through the phase-shift pattern, tothereby decrease an intensity deviation between 0^(th) and 1^(st) orderbeams of the light. The light includes an argon fluoride (ArF) excimerlaser and the transmittance controller includes a diffusion layer havinga diffusion depth of about 100 nm to about 500 nm from a top surface ofthe phase-shift pattern. The phase-shift pattern has a thickness ofabout 400 Å to about 600 Å A from a surface of the transparentsubstrate.

According to another aspect of the present invention, there is provideda method of forming a PSM. A phase-shift layer and a light-shieldinglayer are sequentially formed on a transparent substrate, to therebyform a blank mask on the transparent substrate. A light-shieldingpattern and a phase-shift pattern are formed on the transparentsubstrate by consecutively and partially removing the phase-shift layerand the light-shielding layer. The light-shielding pattern includes afirst opening and the phase-shift pattern includes a second opening thatis connected to the first opening and partially exposes the transparentsubstrate. A transmitting portion is formed in the light-shieldingpattern by partially removing the light-shielding pattern. Thetransmitting portion includes at least one portion of the phase-shiftpattern on which a transmittance controller is formed.

In one example embodiment, the phase-shift layer comprises a materialselected from the group consisting of molybdenum (Mo), molybdenumsilicon (MoSi), molybdenum silicon nitride (MoSiN), molybdenum siliconoxynitride (MoSiON), molybdenum silicon carbonitride (MoSiCN), andmolybdenum silicon carbon oxynitride (MoSiCON), and the light-shieldinglayer comprises a material selected from the group consisting ofchromium (Cr), chromium nitride (CrN), chromium carbide (CrC), andchromium carbonitride (CrCN). In some example, embodiments, thetransparent substrate can comprise quartz, and the blank mask includesan object mask for an attenuated PSM.

In some example, embodiments, forming the light-shielding pattern andthe phase-shift pattern includes: forming a first mask pattern on asurface of the blank mask; partially etching the light-shielding layerusing the first mask pattern as an etching mask, to thereby form thelight-shielding pattern including the first opening through which thephase-shift layer is partially exposed; removing the first mask patternfrom a surface of the light-shielding pattern; and partially etching thephase-shift layer using the light-shielding pattern as an etching mask,to thereby form the phase-shift pattern including the second openingthat is connected to the first opening. The first mask pattern caninclude a photoresist pattern that is formed on the blank mask by aphotolithography process. Etching of the light-shielding layer and thephase-shift layer can be performed by a dry etching process using amixture of chlorine (Cl2) gas and oxygen (O2) gas as an etching gas, orcan be performed by a wet etching process using a mixture of cericammonium nitrate (Ce(NH4)2(NO3)6) and perchloric acid (HClO4) as anetchant.

In some example embodiments, forming the light-shielding pattern and thephase-shift pattern can include: forming a first mask pattern on asurface of the blank mask; partially etching the light-shielding layerand the phase-shift layer sequentially using the first mask as anetching mask, to thereby form the second opening through which thetransparent substrate is partially exposed and the first opening that isconnected to the second opening; and removing the first mask patternfrom a surface of the light-shielding pattern.

In some example embodiments, the transmitting portion may be formedthrough the following example steps. A mask layer is formed on thelight-shielding pattern to a sufficient thickness to fill up the firstand second openings, and the mask layer is partially removed from thelight-shielding pattern, to thereby form a second mask pattern throughwhich at least one light-shielding pattern is exposed. Thelight-shielding pattern exposed through the second mask pattern isetched off using the second mask pattern as an etching mask, to therebyform a preliminary transmitting portion through which the phase-shiftpattern is exposed. Then, a thin layer is formed on the phase-shiftpattern exposed through the preliminary transmitting portion, and amaterial of the thin layer is diffused into the phase-shift pattern.

The light-shielding layer may be removed from the substrate by a dryetching process using a mixture of chlorine (Cl2) gas and oxygen (O2)gas as an etching gas, or by a wet etching process using a mixture ofceric ammonium nitrate (Ce(NH4)2(NO3)6) and perchloric acid (HClO4) asan etchant. Forming the thin layer on the phase-shift pattern caninclude depositing a metal material onto a surface of the phase-shiftpattern exposed through the preliminary transmitting portion using thesecond mask pattern on the light-shielding pattern as a deposition mask.The metal material can have an absorption coefficient of no less thanabout 1.5, and the metal material can include any one selected from thegroup consisting of chromium (Cr), molybdenum (Mo), tungsten (W) andcombinations thereof. The metal material can be deposited onto thephase-shift pattern by a physical vapor deposition (PVD) process such asa sputtering process that is performed using bias power of about 600 Wto about 4,500 W using helium (He) gas or argon (Ar) gas as a sputteringgas. The material of the thin layer may be diffused into the phase-shiftpattern by an annealing process. For example, the annealing process maybe performed in a rapid thermal treatment apparatus using atungsten-halogen lamp as a heat source. Prior to the annealing process,the second mask pattern can be removed from the transparent substrate,so that the transparent substrate is exposed through the phase-shiftpattern.

According to example embodiments of the present invention, atransmittance controller is formed on an upper portion of a phase-shiftpattern of an attenuated PSM, and controls an amount of lighttransmitted to an object substrate, thereby minimizing an intensitydeviation between 0^(th) and 1^(st) order beams of illumination light atthe object substrate. Therefore, the pattern may be uniformly formed onthe object substrate by an exposure process using the attenuated PSMincluding the transmittance controller.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the embodiments of thepresent invention will become readily apparent by reference to thefollowing detailed description when considering in conjunction with theaccompanying drawings, in which:

FIG. 1 is a graph showing intensities of the 0^(th) and the 1^(st) orderbeams diffracted by a conventional attenuated phase-shift mask (PSM);

FIG. 2 is a cross-sectional view illustrating a phase-shift mask inaccordance with an example embodiment of the present invention;

FIGS. 3A to 3G are cross-sectional views illustrating processing stepsfor manufacturing the PSM shown in FIG. 2;

FIGS. 4A and 4B are graphs showing a relationship between the thicknessof a transmittance controller and the intensity of transmitted light;and

FIGS. 5A and 5B are graphs showing process windows and exposurelatitudes of exposure processes in which the PSM including thetransmittance controller is used.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the invention are described more fully hereinafter withreference to the accompanying drawings, in which example embodiments ofthe invention are shown. This invention may, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. In thedrawings, the size and relative sizes of layers and regions may beexaggerated for clarity.

It will be understood that when an element or layer is referred to asbeing “on,” “connected to” or “coupled to” another element or layer, itcan be directly on, connected or coupled to the other element or layeror intervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on,” “directly connected to”or “directly coupled to” another element or layer, there are nointervening elements or layers present. Like numbers refer to likeelements throughout. As used herein, the term “and/or” includes any andall combinations of one or more of the associated listed items.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another region, layer or section. Thus, a first element,component, region, layer or section discussed below could be termed asecond element, component, region, layer or section without departingfrom the teachings of the present invention.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a,” “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

Embodiments of the invention are described herein with reference tocross-section illustrations that are schematic illustrations ofidealized embodiments (and intermediate structures) of the invention. Assuch, variations from the shapes of the illustrations as a result, forexample, of manufacturing techniques and/or tolerances, are to beexpected. Thus, embodiments of the invention should not be construed aslimited to the particular shapes of regions illustrated herein but areto include deviations in shapes that result, for example, frommanufacturing. For example, an implanted region illustrated as arectangle will, typically, have rounded or curved features and/or agradient of implant concentration at its edges rather than a binarychange from implanted to non-implanted region. Likewise, a buried regionformed by implantation may result in some implantation in the regionbetween the buried region and the surface through which the implantationtakes place. Thus, the regions illustrated in the figures are schematicin nature and their shapes are not intended to illustrate the actualshape of a region of a device and are not intended to limit the scope ofthe invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIG. 2 is a cross-sectional view illustrating a phase-shift mask (PSM)in accordance with an example embodiment of the present invention.

Referring to FIG. 2, a PSM 900 in accordance with an example embodimentof the present invention includes a transparent substrate 100 throughwhich illumination light passes, a light-shielding pattern 200 and aphase-shift pattern 300 on the transparent substrate 100 and atransmittance controller 400, or transmittance control pattern, on thephase-shift pattern 300.

For example, the transparent substrate 100 may include a glass substratecomprising quartz, and thus most of the illumination light incidentthereto passes through the transparent substrate 100. An optional,supplementary thin layer such as an indium tin oxide layer may befurther formed on the transparent substrate 100.

The light-shielding pattern 200 for shielding the illumination light andthe phase-shift pattern 300 for shifting the phase of the illuminationlight are positioned on the transparent substrate 100. In the presentembodiment, the phase-shift pattern 300 and the light-shielding pattern200 are sequentially stacked on a top surface of the transparentsubstrate 100.

The light-shielding pattern 200 is positioned on the transparentsubstrate 100, and operates to prevent the illumination light frompassing through the substrate 100. In example embodiments of the presentinvention, the light-shielding pattern 200 may comprise chromium (Cr),chromium nitride (CrN), chromium carbide (CrC) or chromium carbonitride(CrCN). These may be used alone or in combinations thereof. Thelight-shielding pattern 200 includes an opening 280 through which thetransparent substrate 100 is partially exposed, so that the illuminationlight is partially incident onto the transparent substrate 100 throughthe opening 280 of the light-shielding pattern 200. Hereinafter, theopening 280 of the light-shielding pattern 200 is referred to as atransmitting portion 280 of the light-shielding pattern 200. As aresult, the transmitting portion 280 has the same shape as a circuitpattern that is to be transcribed onto a semiconductor substrate for asemiconductor device. Accordingly, the top surface of the transparentsubstrate 100 is partially exposed in correspondence with thetransmitting portion 280, and other portions of the top surface of thetransparent substrate 100 are covered by the light-shielding pattern200. As a result, the illumination light is incident onto thetransparent substrate 100 in accordance with the circuit pattern.

The phase-shift pattern 300 may be interposed between thelight-shielding pattern 200 and the transparent substrate 100, so thatthe phase of the illumination light is shifted before being incidentonto the transparent substrate 100, to thereby control the intensity ofa coherent light due to interference between diffracted beams of theillumination light. Particularly, the light-shielding pattern 200 ispartially removed from the substrate 100, and no light-shielding pattern200 is positioned in the transmitting portion 280 and the transparentsubstrate 100 is partially exposed through the transmitting portion 280.Therefore, only portions of the phase-shift pattern 300 are positionedin the transmitting portion 280, without the light-shielding pattern200.

In example embodiments, the phase-shift pattern 300 may comprisemolybdenum (Mo), molybdenum silicon (MoSi), molybdenum silicon nitride(MoSiN), molybdenum silicon oxynitride (MoSiON), molybdenum siliconcarbonitride (MoSiCN), or molybdenum silicon carbon oxynitride(MoSiCON). These may be used alone or in combinations thereof.

The illumination light incident onto the phase-shift pattern 300 istransmitted through the phase-shift pattern 300 at a giventransmittance, and the phase of the transmitted light is shifted at anangle with respect to that of the incident light onto the phase-shiftpattern 300. When the PSM 900 is used as a mask pattern in an exposureprocess, the illumination light penetrates through the transmittingportion 280 of the light-shielding pattern 200 and the illuminationlight is diffracted by the phase-shift pattern 300. Each of thediffracted beams of the illumination light interferes with one anotherconstructively or destructively on a semiconductor substrate. That is,the illumination light is transformed into a coherent light on thesemiconductor substrate. In the present embodiment, 0^(th) and 1^(st)order beams are mainly used as a light source for exposing thesemiconductor substrate. The 0^(th) order beam indicates the diffractedbeam of the illumination light that does not interfere with any otherdiffracted beams of the illumination light, and the 1^(st) order beamindicates a coherent beam in which the diffracted beams of theillumination light constructively interfere with each other at aposition firstly close to the 0^(th) order beam of the illuminationlight. The phase-shift pattern 300 shifts the phase of the illuminationlight passing through the phase-shift pattern 300 in such a manner thatthe 0^(th) and 1^(st) order beams are exposed to a photoresist film onthe semiconductor substrate at a uniform intensity.

In an example embodiment, the transmittance controller 400 is located onthe phase-shift pattern 300, so that the transmittance of theillumination light that is incident onto the phase-shift pattern 300 iscontrolled. Particularly, the amount of the light passing through thephase-shift mask 300 may be controller by the transmittance controller400, so that the intensity deviation between the 0^(th) and 1^(st) orderbeams may be minimized on the photoresist film on the semiconductorsubstrate.

For example, the transmittance controller 400 may include a diffusionlayer that is diffused to a depth of about 100 nm to about 500 nm from atop surface of the phase-shift pattern 300. The transmittance controller400 may comprise a metal having a large absorption coefficient. In thepresent embodiment, the transmittance controller 400 may comprise ametal having an absorption coefficient of no less than about 1.5.Examples of the metal may include chromium (Cr), molybdenum (Mo) andtungsten (W). In the present embodiment, the phase-shift pattern 300 mayhave a thickness of about 4,000 nm to about 6,000 nm, so that thetransmittance controller 400 occupies about 1.25% to about 8.3% of thethickness of the phase-shift pattern 300 at an upper portion thereof.

According to the PSM 900 of embodiments of the present invention, thetransmittance controller 400 is positioned on the phase-shift pattern300, to thereby control the transmittance of the light passing throughthe phase-shift pattern 300. The intensity of the 0^(th) and 1^(st)order beams, which form the coherent light irradiated onto thephotoresist film on the semiconductor substrate, may be determined inaccordance with the amount of light passing through the phase-shiftpattern 300, so that the transmittance controller 400 may minimize theintensity deviation between the 0^(th) and 1^(st) order beams. As aresult, when the PSM 900 is used as a mask pattern for an exposureprocess, the intensity deviation between the 0^(th) and 1^(st) orderbeams may be sufficiently reduced to thereby improve the uniformity ofthe exposure process to the photoresist film on the semiconductorsubstrate.

FIGS. 3A to 3G are cross-sectional views illustrating processing stepsfor manufacturing the PSM shown in FIG. 2.

Referring to FIGS. 2 and 3A, a phase-shift layer 300 a and alight-shielding layer 200 a are sequentially stacked on the transparentsubstrate 100 through which most of the light passes, to thereby form ablank mask layer on the transparent substrate 100.

For example, the phase-shift layer 300 a may comprise molybdenum (Mo),molybdenum silicon (MoSi), molybdenum silicon nitride (MoSiN),molybdenum silicon oxynitride (MoSiON), molybdenum silicon carbonitride(MoSiCN), or molybdenum silicon carbon oxynitride (MoSiCON). These maybe used alone or in combinations thereof. In addition, thelight-shielding layer 200 a may comprise chromium (Cr), chromium nitride(CrN), chromium carbide (CrC) or chromium carbonitride (CrCN). These mayalso be used alone or in combinations thereof. In the present exampleembodiment, the phase-shift layer 300 a may comprise molybdenum silicon(MoSi), and the light-shielding layer 200 a may comprise chromium (Cr).Further, the transparent substrate 100 may include a glass substratecomprising quartz, and the blank mask may be formed into an attenuatedPSM in subsequent processes.

Referring to FIGS. 2 and 3B, the phase-shift layer 300 a and thelight-shielding layer 200 a are partially removed from the transparentsubstrate 100, thereby forming the light-shielding pattern 200 includinga first opening 220 and the phase-shift pattern 300 including a secondopening 320 that is connected to the first opening 220. The transparentsubstrate 100 may be partially exposed through the first and secondopenings 220 and 320.

In example embodiments, a first mask pattern 500 is formed on thelight-shielding layer 200 a of the blank mask. The first mask pattern500 may include a photoresist pattern that may be formed from aphotoresist film by a photolithography process. Then, thelight-shielding layer 200 a is partially etched off using the first maskpattern 500 as an etching mask, thereby forming the first opening 220through which the phase-shift layer 300 a is partially exposed.Accordingly, the light-shielding layer 200 a is formed into thelight-shielding pattern 200 including the first opening 220. Thereafter,the first mask pattern 500 is removed from the light-shielding pattern200. Then, the phase-shift layer 300 a is partially etched off using thelight-shielding pattern as an etching mask, thereby forming the secondopening 320 consecutively to the first opening 220. Therefore, thephase-shift layer 300 a is formed into the phase mask pattern 300including the second opening 320.

In an example embodiment, the light-shielding layer 200 a and thephase-shift layer 300 a may be etched off by a dry etching process usinga mixture of chlorine (Cl2) gas and oxygen (O2) gas as an etching gas orby a wet etching process using a mixture of ceric ammonium nitrate(Ce(NH4)2(NO3)6) and perchloric acid (HClO4) as an etchant. Thecomposition of the etching gas or the etchant may be varied inaccordance with the composition of the light-shielding layer 200 a orthe phase-shift layer 300 a, as would be known to one of the ordinaryskill in the art.

In another example embodiment, the light-shielding layer 200 a and thephase-shift layer 300 a may be sequentially and continuously etched offby a single etching process using the first mask pattern 500 as anetching mask. The first mask pattern 500 is formed on thelight-shielding layer 200 a, and the light-shielding layer 200 a and thephase-shift layer 300 a are partially etched off sequentially andcontinuously using the first mask pattern 500 as an etching mask,thereby forming the second opening 320 through which the transparentsubstrate 100 is partially exposed and the first opening 220 that isconnected to the second opening 320.

Thereafter, the first mask pattern 500 is removed from thelight-shielding pattern 200 by a strip process.

Referring to FIGS. 2 and 3C, a second mask pattern 600 is formed on thelight-shielding pattern 200, and a transmitting portion is to be formedin the light-shielding pattern 200 in the following processes.

A mask layer (not shown) is formed on the light-shielding pattern 200 toa sufficient thickness to fill up the first and second openings 220 and320, and then a planarization process is performed on the mask layer insuch a manner that the mask layer has a given thickness from a topsurface of the light-shielding pattern 200. The mask layer is partiallyremoved from the light-shielding pattern 200 by a photolithographyprocess, thereby forming the second mask pattern 600 through which thelight-shielding pattern 200 is partially exposed. In the presentembodiment, the processing conditions of the photolithography processare adjusted to sufficiently expose a top surface of the light-shieldingpattern 200, and a top surface of the mask pattern 600 filling up thefirst and second openings 220 and 320 is positioned lower than or equalto the top surface of the light-shielding pattern 200. The removedportion of the mask pattern 600 is formed into a preliminarytransmitting portion 240 in FIG. 3D that is formed into the transmittingportion 280 in FIG. 3F through which the illumination light istransmitted onto the transparent substrate 100 in a subsequent process.

Referring to FIGS. 2 and 3D, the light-shielding pattern 200 is etchedoff from the phase-shift pattern 300 using the second mask pattern 600as an etching mask, thereby forming the preliminary transmitting portion240 through which the phase-shift pattern 300 is exposed. In someexample embodiments, the light-shielding pattern 200 exposed through thesecond mask pattern 600 may be etched off by a dry etching process usinga mixture of chlorine (Cl2) gas and oxygen (O2) gas as an etching gas orby a wet etching process using a mixture of ceric ammonium nitrate(Ce(NH4)2(NO3)6) and perchloric acid (HClO4) as an etchant in a processsimilar to that for forming the first and second openings 220 and 320.The phase-shift pattern 300 can function as an etching stop layer in theabove etching process, so that only the light-shielding pattern 200 isremoved from the transparent substrate 100. The second mask pattern 600in the first opening 220 may also be removed from the transparentsubstrate 100 simultaneously with the light-shielding pattern 200. Whenan etch rate of the light-shielding pattern 200 is the same as that ofthe second mask pattern 600, a top surface of the second mask pattern600 remaining in the second opening 320 is coplanar with a top surfaceof the phase-shift pattern 300. Embodiments of the present invention donot necessarily require that the top surface of the second mask pattern600 in the second opening 320 be coplanar with the top surface of thephase-shift pattern 300, as would be known to one of the ordinary skillin the art. In the present embodiment, the second mask pattern 600 inthe second opening 320 may be formed to have a sufficient thickness forprotecting the transparent substrate 100 in a subsequent depositionprocess for forming the transmittance controller.

Referring to FIGS. 2 and 3E, a thin layer 700 a is formed on thephase-shift pattern 300 and the second mask pattern 600 in the secondopening 320.

In an example embodiment, a metal is deposited onto the phase-shiftpattern 300 and the second mask pattern 600 in the preliminarytransmitting portion 240 by a physical vapor deposition (PVD) process,thereby forming the metal thin layer 700 a on the phase-shift pattern300 and the second mask pattern 600. In the present embodiment, thetransparent substrate 100 including the preliminary transmitting portion240 is loaded into a chamber for a sputtering process in which a metaltarget is positioned. Inert gases such as argon (Ar) gases and helium(He) gases are supplied into the processing chamber and bias power ofabout 600 W to about 4,500 W is applied to the processing chamber. Then,the inert gases are transformed into plasma and the metal of the targetis ionized in the processing chamber. The metal ions are deposited ontotop surfaces of the phase-shift pattern 300 and the second mask pattern600 in the preliminary transmitting portion 240.

For example, the metal may have an absorption coefficient of no lessthan about 1.5. Examples of the metal include chromium (Cr), molybdenum(Mo) and tungsten (W). These may be used alone or in combinationsthereof. The magnitude of the absorption coefficient and the metalhaving the absorption coefficient may be varied in accordance with thewavelength of the illumination light, exposure conditions, and thedesired design rule, size and/or shape of the pattern, so that theembodiments of the present invention should not be limited to theseexample metal materials but various other materials can be used as themetal, as would be apparent to one skilled in the art.

Referring to FIGS. 2 and 3F, the second mask pattern 600 is removed fromthe transparent substrate 100. In a case where the second mask pattern600 includes a photoresist pattern, a strip process may be used forremoving the second mask pattern 600. Particularly, when the second maskpattern 600 in the second opening 320 is removed from the transparentsubstrate 100, the thin layer 700 a on the second mask pattern 600 isalso removed from the transparent substrate 100 simultaneously with thesecond mask pattern 600. Therefore, the transparent substrate 100 ispartially exposed through the second opening 320 and the thin layer 700a remains only on the phase-shift pattern 300, thereby forming a thinlayer pattern 700 on the phase-shift pattern 300. As a result, thetransmitting portion 280 defined by the light-shielding pattern 200 isformed on the transparent substrate 100. The transmitting portion 280includes a first portion 280 a defined by the light-shielding pattern200 and a second portion 280 b including the phase-shift pattern 300 forcontrolling the amount of the light transmitted thereto.

Referring to FIGS. 2 and 3G, a heat treatment is performed on thesubstrate 100 including the thin layer pattern 700, so that the metal inthe thin layer pattern 700 is diffused into the phase-shift pattern 300.As a result, the transmittance controller 400 for controlling the amountof the light transmitted to the phase-shift pattern 300 is formed on thephase-shift pattern 300. The amount of the transmitted light may bedetermined by the material comprising the transmittance controller 400and by the thickness of the transmittance controller 400.

The heat treatment may include a rapid thermal process using atungsten-halogen lamp as a heat source. For example, the heat treatmentmay include an annealing process. The annealing process may be performedat a temperature of about 800° C. to about 1,500° C. for about 3 secondsto about 10 seconds. Accordingly, the metal material of the metal thinlayer 700 may be diffused into the phase-shift pattern 300 at a depthabout 100 nm to about 500 nm.

FIGS. 4A and 4B are graphs showing a relationship between the thicknessof the transmittance controller and the intensity of the transmittedlight. That is, FIGS. 4A and 4B indicate the thickness of thetransmittance controller that minimizes the intensity deviation betweendiffracted beams. FIG. 4A shows experimental results in a case where thepattern size is about 45 nm, and FIG. 4B shows experimental results in acase where the pattern size is about 63 nm. Further, in FIGS. 4A and 4B,numeral I indicates intensity variation of the 0^(th) order beam, andnumeral II indicates intensity variation of the 1^(st) order beam.Various experiments were performed for the results of FIGS. 4A and 4Bunder conditions in which an argon fluoride (ArF) excimer laser is usedas a light source and the phase-shift pattern on which the transmittancecontroller comprising chromium (Cr) is positioned has a thickness ofabout 677 Å.

Referring to FIG. 4A, when an exposure process was performed to form apattern having a half-pitch of about 45 nm using the PSM, the intensitydeviation between the 0^(th) and the 1^(st) order beams continuouslyimproved until the thickness of the transmittance controller increasedto about 380 nm. However, when the thickness of the transmittancecontroller was more than about 380 nm, the intensity deviation betweenthe 0^(th) and the 1^(st) order beams no longer improved. Referring toFIG. 4B, when an exposure process was performed to form a pattern havinga half-pitch of about 63 nm using the PSM, the intensity deviationbetween the 0^(th) and the 1^(st) order beams was minimized when thethickness of the transmittance controller was about 90 nm. In contrast,the intensity deviation between the 0^(th) and the 1^(st) order beamsincreased when the thickness of the transmittance controller was morethan about 90 nm.

Accordingly, the intensity deviation between the 0^(th) and the 1^(st)order beams may be improved by the transmittance controller, and theoptimal thickness of the transmittance controller for minimizing theintensity deviation may be varied in accordance with processingconditions for an exposure process.

The improvement of the intensity deviation between the 0^(th) and the1^(st) order beams may extend an allowable error range of a depth offocus (DOF) and a proper dose of the light for the exposure process, sothat the process window and the exposure latitude of the exposureprocess may be enlarged, thereby increasing the processing margin of theexposure process.

FIGS. 5A and 5B are graphs showing process windows and exposurelatitudes of exposure processes in which the PSM including thetransmittance controller is used. FIG. 5A shows experimental results ofthe exposure process for forming a pattern having a half-pitch of about45 nm, and FIG. 5B shows experimental results of the exposure processfor forming a pattern having a half-pitch of about 63 nm. In FIGS. 5Aand 5B, Graph I shows experimental results of the exposure process usinga conventional attenuated PSM without the transmittance controller, andGraph II shows experimental results of the exposure process using anattenuated PSM including the transmittance controller that compriseschromium (Cr). Graph III shows experimental results of the exposureprocess using an attenuated PSM including the transmittance controllerthat comprises molybdenum (Mo), and Graph IV shows experimental resultsof the exposure process using an attenuated PSM including thetransmittance controller that comprises tungsten (W). In FIGS. 5A and5B, the horizontal axis denotes a DOF of the exposure process, and thevertical axis denotes a dose of the light. The process window of theexposure process is denoted as reference letter A_(i) in each of thegraphs. The process window indicates an allowable range of the dose atan optimal DOF in each of the exposure processes. As a result, as theprocess window becomes larger, the processing margin of the exposureprocess becomes greater. Since the processing margin of the exposureprocess is enlarged, the possibility of processing defects may bedecreased, to thereby improve the reliability of the exposure process.

Referring to FIG. 5A, when an exposure process was performed for formingthe pattern having a half-pitch of about 45 nm, the transmittancecontroller on the attenuated PSM increased the size of the processwindow. That is, the sizes of the process windows A2, A3, and A4 thatwere caused by an exposure process using the attenuated PSM includingthe transmittance controller were much greater than the size of theprocess window A1 that was caused by an exposure process using theattenuated PSM without the transmittance controller. Further, thetransmittance controller also improved the exposure latitude, forexample, from about 10.07% to about 11.70%, 12.15% and 11.86%,respectively.

Referring to FIG. 5B, when an exposure process is performed for formingthe pattern having a half-pitch of about 63 nm, the transmittancecontroller on the attenuated PSM also increased the size of the processwindow. That is, the sizes of the process windows A6, A7, and A8 thatwere caused by an exposure process using the attenuated PSM includingthe transmittance controller were much greater than the size of theprocess window A5 that was caused by an exposure process using theattenuated PSM without the transmittance controller. Further, thetransmittance controller also improved the exposure latitude, forexample, from about 10.34% to about 11.15%, 11.71% and 11.26%,respectively.

Accordingly, the presence of the transmittance controller on thephase-shift pattern can operate to improve the process window andexposure latitude of the exposure process as well as decrease theintensity deviation between the 0^(th) and the 1^(st) order beams.

According the example embodiments of the present invention, atransmittance controller comprising a metal is formed on an upperportion of a phase-shift pattern of an attenuated PSM, therebyminimizing an intensity deviation between 0^(th) and 1^(st) order beamsof illumination light at a photoresist film on a semiconductorsubstrate. In addition, the transmittance controller of the attenuatedPSM may also improve the size of a process window and the size of anexposure latitude in an exposure process, thereby increasing theprocessing margin of the exposure process. As a result, the processreliability of an exposure process may be sufficiently increased despitea small pattern size, so that a minute pattern may be formed on asemiconductor substrate with sufficient accuracy.

Although the example embodiments of the present invention have beendescribed, it is understood that the present invention should not belimited to these example embodiments but various changes andmodifications can be made by one skilled in the art within the spiritand scope of the present invention as hereinafter claimed.

1. A phase-shift mask (PSM), comprising: a transparent substrate throughwhich light passes; a light-shielding pattern that is positioned on thetransparent substrate and prevents the light from being incident ontothe transparent substrate, the light-shielding pattern defining atransmitting portion through which the transparent substrate ispartially exposed and the light is incident onto the transparentsubstrate; a phase-shift pattern that is positioned on the transparentsubstrate exposed through the transmitting portion, the phase-shiftpattern shifting the phase of the light that passes through thetransmitting portion; and a transmittance controller that is positionedat an upper portion of the phase-shift pattern in the transmittingportion and controls the transmittance of the light with respect to thephase-shift pattern in the transmitting portion.
 2. The PSM of claim 1,wherein the transmitting portion has a shape corresponding to a circuitpattern that is to be transcribed onto a semiconductor substrate formanufacturing a semiconductor device.
 3. The PSM of claim 1, wherein thephase-shift pattern comprises molybdenum (Mo) and the light-shieldingpattern comprises chromium (Cr).
 4. The PSM of claim 1, wherein thetransmittance controller includes a material selected from the groupconsisting of chromium (Cr), molybdenum (Mo) and tungsten (W), andcontrols the transmittance of the light passing through the phase-shiftpattern, to thereby decrease an intensity deviation between 0^(th) and1^(st) order beams of the light.
 5. The PSM of claim 1, wherein thelight includes an argon fluoride (ArF) excimer laser and thetransmittance controller includes a diffusion layer having a diffusiondepth of about 100 nm to about 500 nm from a top surface of thephase-shift pattern.
 6. The PSM of claim 5, wherein the phase-shiftpattern has a thickness of about 400 Å to about 600 Å from a surface ofthe transparent substrate.